1. Field of the Invention
The present invention relates to a hologram screen for producing full-color or monochromatic still image or moving image by projecting image-forming light.
2. Related Art
There has heretofore been known a hologram screen for producing advertisements such as of moving image or still image by sticking it onto a show window or the like, and projecting image-forming light 3 from a projector 2 as shown in FIGS. 15A and 15B.
The hologram screens can roughly be divided into a transmission-type hologram screen 9 which permits the image-forming light 3 to pass through as shown in FIG. 15A and a refection-type hologram screen 90 which reflects the image-forming light 3 as shown in FIG. 15B.
That is, the transmission-type hologram screen 9 shown in FIG. 15A comprises a transparent member 91 and a transmission-type hologram film 92 stuck to the transparent member 91, and the reflection-type hologram screen 90 shown in FIG. 15B comprises a transparent member 91 and a reflection-type hologram film 920 stuck to the transparent member 91.
The transmission-type hologram screen 9 and the reflection-type hologram screen 90 are used depending upon their respective applications. Namely, the transmission-type hologram screen 9 is used in an application where a viewer E2 views the image from the side opposite to the projector 2 as shown in FIG. 15A. This can be represented by, for example, the one where advertisements are to be displayed in front of the shop.
On the other hand, the reflection-type hologram screen 90 is used in an application where a viewer E1 views the image from the side of the projector 2 as shown in FIG. 15B. This can be represented by, for example, one where advertisements are to be displayed inside the shop.
Demands, in the market, are increasing for both of these hologram screens.
However, production of the above-mentioned hologram films 92 and 920 requires precise and large-scale optical systems for exposure to light as well as a highly sophisticated technology. Besides, the transmission-type hologram film 92 and the reflection-type hologram film 920 are produced requiring different kinds of optical systems for exposure to light and different kinds of production technology. Therefore, it is difficult to produce both the transmission-type hologram film 92 and the reflection-type hologram film 920, and a tremendously large cost of investment and cost of development are needed if both of them are to be produced.
It has therefore been desired to produce not only the transmission-type hologram screen but also the reflection-type hologram screen by using the transmission-type hologram film 92.
The present invention was accomplished in view of the problems inherent in the above prior art, and its object is to produce a hologram screen that can be easily produced by using the transmission-type hologram film enabling the image to be seen from the side of the projector.
The present invention is concerned with a hologram screen having a transparent member and a hologram film stuck to the transparent member and producing image by projecting image-forming light from a projector, wherein:
the hologram film is a transmission-type hologram film; and
a reflector for reflecting the image-forming light is arranged on the back surface side of the hologram film.
In the present invention, what draws the greatest attention is that the hologram film is the transmission-type hologram film, and that a reflector for reflecting the image-forming light is arranged on the back surface side of the transmission-type hologram film.
The reflector may be the one which totally reflects the image-forming light or may be the one which permits part of the image-forming light to pass through.
In connection with the hologram film and the like in this specification, the side on where the projector is arranged is referred to as xe2x80x9cfront surface sidexe2x80x9d and the opposite side is referred to as xe2x80x9cback surface sidexe2x80x9d.
Further, the projector is, for example, a liquid crystal projector, and the image may be, for example, a full-color or monochromatic still image or moving image.
The hologram film may be directly stuck to the transparent member, or may be stuck to the transparent member via any other member such as the above-mentioned reflector or the like. The reflector may be directly stuck to the back surface of the hologram film (see embodiment 1) or may be stuck to the back surface of the transparent member (see embodiment 2).
Next, the operation and advantage of the invention will be described.
The above-mentioned hologram film is a transmission type hologram film. Therefore, when an image light is projected from an upper diagonal direction onto the hologram film, for example, the image light is diffracted and scattered on the hologram film to pass therethrough in a substantially horizontal direction.
Since the reflector is arranged on the back surface side of the hologram film, the image-forming light passing through the hologram film is reflected in a substantially horizontal direction.
Therefore, the image light travels to the front surface side of the hologram screen. Thus, a viewer at the front surface side of the hologram screen can see the image.
As such, since the hologram screen is constructed of the transparent-type hologram film stuck to the transparent member, the image can be recognized from the side of the projector. Therefore, even though the transparent-type hologram film is employed, the hologram screen functions as a reflection-type hologram screen.
On the other hand, the hologram screen can be used as a transparent-type hologram screen by which an image can be recognized at the side opposite to the projector. That is, by using a hologram film for manufacturing a transparent-type hologram screen, the hologram film having a reflecting function can be easily manufactured.
Therefore, there is no need of making an investment or developing the technology for particularly producing the reflection-type hologram screen, and the hologram screen can be cheaply produced.
Besides, the background light from the side opposite to the viewer passes through the hologram screen to some extent provided the reflector is not the one which totally reflects light. Therefore, the viewer is allowed to see, as a background, the opposite side of the hologram screen.
According to the present invention as described above, the hologram screen can be easily produced by using the transmission-type hologram film, the hologram screen enabling the image to be seen from the side of the projector.
According to the second aspect of the present invention, the hologram film may be so arranged as to produce an image on the front surface side of the hologram screen by permitting the image-forming light directly projected from the projector to pass through without causing it to be diffracted, and by diffracting the image-forming light that is reflected by the reflector after having passed through the hologram film (embodiment 4, FIG. 9).
In this case, the image can be produced on the front surface side only of the hologram screen so will not to be viewed from the back surface side.
According to the third aspect of the present invention, it is desired that the reflector is arranged between the hologram film and the transparent member.
Thereby, the reproduced images are not overlapped one upon the other by the reflection by the front surface and the back surface of the transparent member, and a favorable image is obtained.
According to the fourth aspect of the present invention, the reflector is one obtained by directly coating the transparent member with a metal or a nonmetal, one obtained by sticking a metal-coated resin film onto the transparent member, or one obtained by sticking a metal foil onto the transparent member.
Thus, it is allowed to obtain a reflector which efficiently reflects the image-forming light and to easily produce the hologram screen.
As the above metal, there can be used, for example, aluminum, silver, gold or chromium. As the nonmetal, there can be used zinc sulfate or cerium oxide. As the resin film, there can be used a polyester or a polyethylene terephthalate.
As means for coating the transparent member or the resin film with a metal, there can be employed chemical plating, vacuum evaporation or sputtering.
According to the fifth aspect of the present invention, it is desired that the transparent member is a resin or a glass.
This makes it possible to cheaply obtain the hologram screen for reflecting image maintaining good quality. When the transparent member is a resin, there is obtained a hologram screen which is light in weight.
As the above resin, there can be used a polycarbonate, acrylic or vinyl chloride.
According to the sixth aspect of the present invention, it is desired that a light-scattering film is disposed on the front surface side of the hologram film to scatter the image-forming light.
This makes it possible to impart some degree of angular width to the image-forming light incident on the hologram film. Accordingly, the image is obtained as the image-forming light is diffracted by the hologram film, excellently reproducing the colors.
Further, the so-called 0-degree light traveling straight through the hologram film from the projector, can be scattered through the light-scattering film. This prevents the 0-degree light from entering into the eyes of the viewers.
According to the seventh aspect of the present invention, the reflector may be the one which totally reflects the image-forming light.
In this case, there is obtained a hologram screen of the reflection type which enables the image to be viewed from the front surface side where the projector is disposed.
According to the eighth aspect of the present invention, further, the reflector may be the one which permits part of the image-forming light to pass through.
In this case, part of the image-forming light diffracted by the hologram film transmits to the back surface side permitting the image to be viewed by even a viewer on the back surface side. Therefore, the image can be viewed from both the front surface side and the back surface side of the hologram screen.
According to the ninth aspect of the present invention, it is desired that the reflector has a light transmission factor of from 20 to 50% or a light reflection factor of from 30 to 60%. This enables the image reflected by the hologram screen to be viewed more easily.
When the light transmission factor is smaller than 20%, it may become difficult to view the image from the back surface side of the hologram screen. When the light transmission factor exceeds 50%, on the other hand, it becomes difficult to view the image from the front surface side of the hologram screen.
When the light reflection factor is smaller than 30%, it may become difficult to view the image from the front surface side of the hologram screen. When the light reflection factor exceeds 60%, on the other hand, it may become difficult to view the image from the back surface side of the hologram screen.
According to the tenth aspect of the present invention, further, it is desired that the hologram screen has a reflection-preventing film on at least either the front surface side or the back surface side thereof.
This makes it possible to prevent the reflection of the background light on the front surface or the back surface of the hologram screen. This prevents the background on the same side as the viewer from being reflected on the hologram screen and from being superposed on the image. Accordingly, there is obtained a hologram screen reflecting easy-to-see images.
Next, according to the eleventh aspect of the present invention, a relationship,
60xc2x0xe2x88x92tanxe2x88x921 {Lxc3x97tan 60xc2x0/(L+d)}xe2x89xa60.5xc2x0
is satisfied by a distance L between the hologram screen and the viewer on the side of the front surface thereof, and by a distance d between the hologram film and the reflector (embodiment 5, FIG. 10).
In this case, noise is not seen by the observer on the front surface side of the hologram screen, and a drop in the quality of image is avoided. When the above-mentioned relationship is not satisfied, the noise may be perceived.
According to the twelfth aspect of the present invention, it is desired that the reflector is detachably attached to the transparent member and to the hologram film (embodiment 6, FIG. 11).
In this case, the hologram screen can be easily changed over into the one of the transmission type or into the one of the reflection type depending upon the use.
According to the thirteenth aspect of the present invention, it is desired that the reflector is arranged on a portion of the whole hologram film (embodiment 7, FIG. 12).
In this case, it becomes possible to reflect different images on the front surface side and on the back surface side of the hologram screen (FIGS. 13 and 14).